(116) 
and their accumulation forms peat. The “black mosses’ 
(Andreaea) differ from both of the other groups in the 
valvular capsule; they grow on dry rocks. The true mosses 
vary exceedingly in size and aspect. An examination of 
the specimens in the exhibition cases will convey to the 
mind a better idea of this group than may be gained from 
a description. They grow under all kinds of conditions 
from dry rocks to deep water. Many of the kinds grow on 
almost any kind of rock, earth, or bark of trees, while 
certain ones are more particular as to their habitat. Some 
will thrive only on limestone, which they often gradually 
disintegrate and partially preserve in the masses of closely 
set plants as a calcareous tufa; other species prefer ground 
that has recently been burnt over, as species of Funaria 
and Leptobryum, while others grow only on the bones of dead 
animals or in places where animal refuse has accumulated. 
Next higher in the plant kingdom is the subkingdom 
Pteridophyta, or ferns and fern-allies, the seedless plants 
with roots, stems, leaves, and woody tissue (cases 51 to 
55). The ferns as a group perhaps attract the attention 
of a greater number of people than any other series of 
plants. Associated with what are usually known as ferns 
are the fern-allies, for example the “‘horse-tails” (Equi- 
setum), “‘lycopods” (Lycopodium), and ‘“quillworts” (Iso- 
etes), but these are usually less conspicuous than the 
“ferns.”” Fern-plants differ from all the plants of simpler 
organization in having vascular (woody) tissue, that is, 
a system of vessels for conducting sap through the different 
parts of the plant-body. They exhibit an almost infinite 
variety of form; their stems may be underground, hori- 
zontal on the ground, or erect; the leaves are either simple 
or compound, and sometimes perform both the work of 
foliage leaves and that of bearing the spore-cases (ferns), 
while in other cases some of the leaves have become changed 
into mere spore-bearing organs (cinnamon-fern). 
The “flowering” plants (cases 56 to 128) comprise a 
single subkingdom, the Spermatophyta, or seed-bearing 
